New oleopneumatic invention traction roller Dyneema

I cant get the links to work? anyone else?

When I saw the first picture, for a split second I thought it was a vacuum cleaner

I'm having a little difficulty in understanding how it works, but how I see it, you load it like a conventional band gun, but the energy comes from pneumatic thingamajigs inside, no?

I love the sleek lines and how futuristic it looks!
But I'd believe it's functions when I see it in action

got it open, love the concept!! Hope they build one soon

The "Dreamair" speargun uses long wishbone cables to rotate external drums or pulleys on each outer end of the axles located in the muzzle. There have been proposed versions of the "Dreamair" using 1, 2, 3 and 4 axles, each of which has its own set of wishbone cables. These cables spiral wind on the outer drums so that when the gun is fired each side of the cable has its full length rapidly coiled around its respective drum leaving only the vee-shaped ends which you pull on to load the gun sitting above the spear guide track. The muzzle interior and the barrel is essentially a long pressure tank with a sliding piston sitting at the rear end of the barrel tube. This large cross-section piston is dragged forwards in the barrel tube when the cable wishbones are pulled back to cock the gun as the rotating axles in the muzzle co-axially mount an inner drum which winds in an inner cable connected to the front end of the moving piston just as the external cables are unwinding on each side from their outer drums. Dragging the piston forwards in the gun reduces the volume and increases the pressure in the forward section of the barrel while the barrel space located behind the departing piston develops a vacuum. The idea is that when the gun shoots the higher pressure in the front section of the gun can push the piston back with nothing behind the piston to impede its return to the rear position in the barrel. If the rear section of barrel was allowed to flood then water being pushed out of the gun by the returning piston would absorb power from the shot, hence the pressure tank is sealed off from the environment at both ends, front and rear, creating a completely closed system.

The axles and inner drums are located in the high pressure area, being inside the tank, which means that the axles have to protrude through dynamic pressure seals in order to have the outer drums mounted on their exposed ends. Given that the axles rotate at high speeds during the shot the sealing here is critical or the gun will lose high pressure air from around the spinning axles. If air leaks past the sliding piston then the vacuum developed at the rear will be lost, yet because the tank is completely sealed there would be no external indication of this happing until you pulled the trigger. For the piston to fully return to the rear of the barrel after the shot any pressurized air inside the gun has to remain in front of the piston, otherwise the piston will only move back until it reaches a position where the pressure on the front and rear piston faces equalizes.

Another critical aspect is that the cables accurately wind on and off their drums keeping to the spiral cable tracks formed in the inner and outer drums; during loading that may not be a problem, but they also have to do it at high speed during the shot. If the cables don't stay in the tracks then there will be problems like uneven cable pull from side to side and possibly tangles and jamming of the cables. The "Dreamair" has many moving parts when you consider the sets of inner and outer cables, the spiral track inner and outer winding drums and their axles and a much larger sliding piston than is usual for a pneumatic speargun (more friction on the larger periphery seals). The stored energy from loading effort has to move all these extra parts as well as propel the spear which will adversely affect the efficiency of the gun. Then all the internal and external cable connections need to have reliable anchor points on their respective drums so that forces transmit reliably from the cables through the drums and axles with the cable lengths all being properly adjusted, especially on the multi-axle versions.

A working gun may be possible, but its efficiency and long term reliability is open to question when so many parts need to move and function exactly as intended, particularly the cables moving laterally as they track across the grooves in the winding drums because the groove flanges are all that is directing them and for that to happen the cables need to remain taut on the drums.

A single wishbone cable/axle version would be just as powerful as the multi-axle versions which only serve to break up the loading effort. This is because pulling the first wishbone on a dual axle gun advances the piston for half of its travel, then pulling the second wishbone advances the piston for the other half of its travel to the fully cocked position. On a four axle gun each wishbone draw only advances the piston by a quarter of its travel. On a three axle gun this would involve one wishbone draw performing a half piston travel and the other two wishbones performing a quarter piston travel each. A system of sub-pulleys on the inner cables arranged in a block and tackle fashion creates this incremental loading of the piston, but this adds to the task of setting up all the cables inside the gun and securing all the cable ends with their pulley connections.

Here is a drawing of a two axle version showing the inner works.

The four axle version (a standard pneumatic gun is shown at the bottom as a comparison).

Thank you for explaining, pete.

How the sub-pulley system on the inner cable operates for extra axles.

Thank you Pete.

The real question is even if everything works as intended does it result in a more powerful/accurate/easy to handle/affordable speargun.

Quote from Dan

Thank you Pete.

The real question is even if everything works as intended does it result in a more powerful/accurate/easy to handle/affordable speargun.

On face value I don't see this as being a very efficient or reliable weapon, but the proof will be when one is actually tested. The short piston stroke uses about half the length of the gun compared to a standard pneumatic, but it has a much bigger piston. I think the gun would be expensive to make and assemble compared to other spearguns. However the imagination displayed and styling is certainly worth looking at, but the protracted development time indicates some problems. The KISS principle works best when designing spearguns as there are less parts to go wrong.

Looking at the numbers on the diagram makes me wonder how achievable they are. The stated loading effort starts at 120 kg (264.6 pounds) and ends at 60 kg (132.3 pounds), that is a pretty big loading effort, yet is the complete reverse of the usual loading force distribution where the start effort is less than that at the end of loading, not greater. If the air pressure in the gun is 11 atm (gauge) and it has a piston of 10 sq. cm. cross-section then the force on the piston at the start of loading is 110 kg and at the end of loading is 220 kg, assuming that the "Dreamair" gun has a compression ratio of around 2. The piston looks like it moves half way up the barrel to the fully cocked position, thereby halving the volume which results in a doubling of air pressure inside the gun. As the pressure vessel is closed off from the environment and there is a vacuum with the gun cocked I suppose we should consider the absolute pressure rather than gauge pressure, in which case the gun pressure will be 12 atm absolute and start and end forces will be 120 kg and 240 kg respectively. That 120 kg figure lines up with the start figure on the diagram, but the end figure of 240 kg is four times the stated end value of 60 kg which requires a 4:1 ratio of the outer drum to inner drum diameters to reduce the force in the wishbone cable. Based on the forces acting on the piston and a travel distance of 0.5 metre the gun should store 900 joules which is also the figure quoted for the CVT system on the diagram. Hence no losses are calculated for the CVT system or any friction losses associated with the moving piston, although these calculations are based on a compression ratio (CR) of 2 and that is only an assumption on my part. The proportions on the gun schematic indicate that the CR may be less, but a figure of 2 provides the 900 joules result based on the piston's energy storage. The areas of the green and red bordered shapes on the diagram represent the energy stored; a joule is a Newton-metre and a Newton is a kilogram force multiplied by 10 (actually 9.8, but 10 is close enough for our purposes here).

Doubling the pressure doubles the load on the sliding piston with the gun cocked and the inner cable attachment to the piston has to bear all that load. At 11 atm (12 atm absolute) that final load was 240 kg, at 23 atm (24 atm absolute) the final load will be 480 kg. I don't think that is very realistic. A dual axle gun has the inner cable doubled up around the pulley located on the face of the piston, hence two cable strands then run back to the piston to share the load rather than one strand with the single axle version (refer to the earlier "inner cable system" diagram), but now the pulley axle which the inner cable runs around and its mounting position on the piston have to withstand that load.

The increased pressure 11 to 23 atm (12 to 24 atm absolute) doubles the stored energy, the use of dual axles separates the loading effort into two parts, but they are not equal parts. To understand this we only need consider the piston being moved. The first wishbone draw will move the piston to the halfway point of the fully cocked gun. Hence with 24 atm absolute in the gun the pressure will provide 240 kg at the start and 360 kg (multiply start figure x 1.5) at the end acting on the inner cable attachment to the piston. The second wishbone draw will then move the piston from that halfway point to the fully cocked position, that will be 360 kg at the start and 480 kg at the end acting on the inner cable attachment to the piston. These calculations are simply made as the compression ratio dictates the pressure changes in the gun.

Thus subsequent wishbone draws commence at higher pressures and higher loads as the piston progressively moves, they cannot all start at the same load because the pressure in the gun increases with each loading step of the piston movement. I cannot see a CVT system bringing about a change in this situation as each outer drum on multi-axle versions of the gun should have the same spiral track form so that the wishbone cables unwind and wind in a synchronized movement, they cannot have variable "gearing" as they all shoot together even though they load separately.

If we go back to the 11 atm (12 atm absolute) example and have four axles and four wishbone cables on that gun then the gun will still only store 900 joules, but loading will then move the piston in quarter steps. The pressure will start at 12 atm (120 kg load) and move to 15 atm (150 kg) on the first wishbone draw, on the second draw it will start at 15 atm and move to 18 atm, the third draw will move that value up to 21 atm and the fourth and final draw will result in a pressure of 24 atm. Thus wishbone loadings start from 120 kg, 150 kg, 180 kg and 210 kg respectively for wishbones 1, 2, 3 and 4 in terms of the force on the inner cable. For the 23 atm (24 atm absolute) example you double all the above numbers. On a two axle version you omit the second and third draw figures, therefore the numbers are first draw 240 kg to 360 kg, second draw 360 kg to 480 kg on the inner cable system.

Even with a CVT system the piston loads dictate what can be done with the gun in a practical sense and there is a limit to physical drum sizes and spiral track profiles as ultimately the spiral track length has to accommodate the length of cable being wound on an off. A longer gun would need wider drums to provide more track length in the grooves for the longer cables. Spiral track drums would need to be synchronized from side to side on the axles so that they are at the same rotation, they cannot be out of phase, ditto for drums on multi-axle versions. Thus the design becomes a lot more complicated to make than it may appear on initial inspection and I doubt that CVT system would be able to deliver the performance expected. However cylindrical drums may work with a constant transmission, the outer drums being double the inner drums in terms of diameter so that for the same number of turns of the axle the outer drums let out double the length of cable that the inner drum winds in and vice versa.

I'v been using for several years pneumatic guns on the Med Sea coast...
usually we load the gun by holding the shaft in the right hand, gun barrel in the left hand, then we do pushing at the same time the shatf and the gun with the fin by kneeling...
and you?
does it work better with this innovation?